I asked a while ago, how to build an automatic light switch and finally got around to actually building it.
My board is an ESP8266 mini D, and ignoring all the sensor parts, my problem right now is powering the actual light.
It's just a small LED array and I connected it directly to the 5V and GND pins (controlled via a transistor).
Measuring from the wall (so including the PSU), this whole setup pulls about 3W (so far expected), however, one small component close to the USB connector gets uncomfortably warm, and I'm not sure, whether that's ok.
The hot component is one of the two small thingies circled in the picture. I thought the 5V get pulled directly from the USB plug, so I'm not sure, why there is any circuitry involved.
The voltage regulator is only used to generate the 3.3V supply for the ESP. But OP is using the 5V from the input of the regulator to power the LEDs.
At max it is wasting about 0.7W if the 400mA max current is right. But it will still get hot due to the current draw of the ESP. Even at half of the max. rated current this device is probably 30-40 degrees above your ambient temperature.